Well, the numbers are crunched, and they look encouraging. With a custom piston added to the mix, the gun will handle a 20" .25 barrel... at 50% valve to barrel volume. An expert WAG (not mine... a real expert) puts the max output (determined by port size, our max is 4mm) at ~ 30fpe.It will be interesting to see what can be done with a .25 10" barrel. This gun will have real usefulness as a hunter of real pests.
How many pumps to 30fpe?
Quote from: stalwart on August 03, 2015, 08:05:10 PMWell, the numbers are crunched, and they look encouraging. With a custom piston added to the mix, the gun will handle a 20" .25 barrel... at 50% valve to barrel volume. An expert WAG (not mine... a real expert) puts the max output (determined by port size, our max is 4mm) at ~ 30fpe.It will be interesting to see what can be done with a .25 10" barrel. This gun will have real usefulness as a hunter of real pests.http://www.gatewaytoairguns.org/GTA/index.php?topic=86793.msg858044#newWith a 25% valve and a 20" .25 barrel I got 38 FPE (806 FPS) with 38 pumps in a crosman 1400 tube and 25.4 gr pellets. i also got 30 FPE at 23 pumps. My pump tube volume is 30 cc and my valve volume is 4 cc.Hope this helps.
With an 8cc total volume (50%), we should get about 35cc of swept volume. This is for the eventual carbine... a .25 pistol (10") will leave us with about 45cc.
I'm doing all my designing based on a max of 50%... and hope to offer a few volumes so a guy can tailor his gun to his use. I figure more than 8cc will never see use, and the choice of volumes may end up in 1.5 or 2cc increments.I'm using the stock (25mm dia) tube.The less volume a guy chooses, the less pumps it will take to get each cc up to pressure... as I'm stealing valve volume from swept volume.As I've said before, I'm in this for the long haul. I plan to offer these, and more goodies, as soon as I'm happy with their performance. I'm not only designing these mods for effect, but put a lot of thought into designing for cost effective manufacture.We still haven't hit the apex of the developmental curve of these guns. Lots more fun to be had...